Last year, Krohn and his wife, Peggy Krohn, founded two Arkansas chapters of FrogWatch USA, a citizen science program of the Association of Zoos and Aquariums.

Tom Krohn said the soundtrack is a great disservice to the 23 varieties of frogs and toads that live in Arkansas. They make a symphony of sounds, from the bellowing bass of American bullfrogs to the soprano chirping of spring peepers.

Frogs are making all this racket for a good cause, of course: They're trying to attract mates.

“FrogWatch USA is a national, long-term acoustical survey of breeding frogs and toads,” according to Frog-Watch's national website, aza.org/frogwatch.

Tom Krohn travels the state putting on presentations about the auditory aspects of anurans, the taxonomic order that includes frogs and toads. During the hour-long lecture, he teaches attendees to mimic the sounds of four Arkansas anurans: the American bullfrog, the spring peeper, Fowler's toad and the dwarf American toad, which Krohn described as the “most musical of all the toads we have in Arkansas.”

When a crowd of about 20 people croaked, trilled and peeped in chorus for Krohn last month at the Boone County Library in Harrison, it was a bit more cacophonous than one might expect on a spring night in the Ozark Mountain wilderness, with some of the frogs sounding a lot like sheep. But for a first try, Krohn said, the group was pretty good.

“Give yourselves a hand,” he told them. “If you hear that out on your farm, give me a call. I want to come out and hear it for myself.”

The imitating exercise wasn't just for fun. Frog-Watch has a serious mission.

“It is estimated that at least one-third of known amphibian species are threatened with extinction,” according to FrogWatch's Facebook page. “You can be directly involved in gathering information that may help stop the decline of these important and treasured animals.”

FrogWatch has 103 chapters in 38 states and the District of Columbia, said Shelly Grow, director of conservation programs for the Association of Zoos and Aquariums in Silver Spring, Md.

It started the chapter program in 2010. Since then, FrogWatch chapters have trained more than 3,000 people to discern the sounds made by different types of frogs and toads, she said.

“FrogWatch gets more people involved, and people choose a spot that's convenient to monitor or that is interesting to them,” she said.

So far, 80 different species of frogs and toads have been identified in the U.S. Arkansas has 23 of them.

“All through the Southeast is fantastic for amphibian diversity,” Grow said. “Oregon only has three.”

The Arkansas chapters have trained 128 volunteers and have about 40 monitoring sites, Krohn said.

FrogWatch volunteers listen to anurans outdoors at night to get an idea of how many and what type are in the area.

In Arkansas, FrogWatch monitors anuran sounds from February to August each year. They listen for three minutes, then estimate intensity and species.

“That's how we monitor the numbers,” said Krohn. “We don't count them. We don't see them because we're out there at night.”

Grow said there's no need to count all the frogs in an area.

“We're trying to figure out if they're present in an area - if it's a large group of them or just a few individuals,” she said.

If silence falls over the frogs at night, Krohn said, he can sometimes imitate one to get them to start croaking and trilling again. That's why he teaches volunteers to call the frogs.

“Mimicking is actually a really good way to remember that species or learn that species,” said Grow.

Krohn said frogs and toads can live six to eight years in the wild and up to 18 years in captivity.

“They've been around for 220 million years, so they have a pretty successful breeding rate,” said Krohn.

The frog and toad population in Arkansas appears to be healthy, Krohn said.

A Sign Of Trouble

Anurans play an important role as both prey and predator in wetland ecosystems and are considered indicators of environmental health, according to the national FrogWatch website.

“Many previously abundant frog and toad populations have experienced dramatic population declines both in the United States and around the world, and it's essential that scientists understand the scope, geographic scale, and cause of these declines,” a message on the website states.

Frogs and toads are at risk because of habitat loss, pollution and chemical contamination, environmental changes, disease and harvesting, Krohn said.

Frogs can take in oxygen and water through their skin, so they're particularly sensitive to water quality, said Krohn.

“Anything wrong with the environment is going to go right into that frog through its skin,” he said.

The meeting in Harrison was just for people to get their feet wet. If they're interested in taking the next step in frog conservation, they can take a training session in which they learn about the sounds of all anurans that might be in their area.

If a person learns the sounds of the anurans on his property, and the number or variety decreases, it could signal an environmental concern such as pollution or a disease that affects frogs, said Krohn.

Peculiar Aspects

The American bullfrog is the largest frog in Arkansas, growing to about 8 inches in length, Krohn said. Initially, it was found only on the East Coast, said Krohn, but “because frog legs taste good,” people began exporting bullfrogs across the country, and some of them inevitably got loose. Now, they can be found across the eastern U.S. and part of Canada and Mexico.

Bullfrogs can be hunted in Arkansas from April to December each year, said Krohn. Eighteen a day can be bagged for personal use.

“It's illegal for us to take any other kind of frog out of the environment,” he said.

In addition to being tasty, bullfrogs have a hearty appetite. They even eat birds, Krohn said.

“The acid in a bullfrog's stomach is extremely strong,” he said. “It'll digest feathers and claws and beaks, whatever you shove into it, even the end of your finger.”

Krohn said frogs don't cause warts, but there are some unusual facts about them.

Frogs use their eyeballs to help them swallow food, said Krohn. The eyeballs drop into the cranial cavity and help the frog push food down its throat.

And their ability to leap is proportionally impressive. A 1-inch frog can leap 6 feet. A frog the size of a man would be able to leap the length of a football field, said Krohn.

Spring peepers are already out this year, with their periodical peeps harmonizing into a constant chorus, said Krohn. Other frogs premiere later in the spring.

Krohn said he's encouraging Arkansans to go outside and listen to the frogs. Otherwise, if something happens in the future and the frogs are gone, people won't know what they're missing.

“Mainly I just want to get people excited about being outside,” said Krohn. “So take your kids and grandkids out to listen to them.”

Free FrogWatch training workshops are scheduled for:

Friday at the Janet Huckabee Arkansas River Valley Nature Center in Fort Smith